Type IV Monteggia fracture in a cat.

A one-year-old neutered male cat was referred for a grade IIIA open radius and ulna fracture. The mid-diaphyseal radial and ulnar fractures were associated with lateral radio-humeral and radio-ulnar dislocations. From these abnormalities, a diagnosis of type IV Monteggia fracture was made. The annular ligament was found to be intact on examination and the radial head was correctly positioned and stable after fracture reduction and plate fixation. Eighteen months postoperatively, the cat did not exhibit any signs of lameness or any signs of pain on palpation and mobilisation. Signs of mild osteoarthritis were present on radiographs. Type IV Monteggia fractures are very rare in animals. The combination of a radial head dislocation with an intact annular ligament is uncommon. This pattern allowed a single reconstruction with two plates without a radio-ulnar screw.